From Dr. Lauren Deville - Naturopathic Doctor

Image by Shingo_No from Pixabay

Vitamin K is a fat-soluble vitamin best known for its role in blood clotting—in fact, the “K” stands for “koagulation” (the Danish spelling of the word).

While Vitamin K is fat-soluble, the body doesn’t store much of it, so we have to consume it on a regular basis. Our bodies can also recycle the Vitamin K we have, which means we don’t have to consume as much of it as we otherwise might.

Functions of Vitamin KAs mentioned, Vitamin K is necessary for producing several clotting factors, produced in the liver. (As such, the anti-coagulant medication Warfarin works by preventing Vitamin K recycling.)

Vitamin K also helps to make sure that calcium gets stored where it should be (in the bones, including the teeth), and doesn’t instead deposit where it shouldn’t be (the tissues and arteries). Because of this, higher Vitamin K intake is associated with improved bone density, and also with less vascular calcification–and thus, decreased heart disease risk.

Proteins that require Vitamin K are present in cartilage as well as bone, which may be why it is beneficial for osteoarthritis as well.

In addition to all of this, Vitamin K has a role in regulating oxidative stress and inflammation.

Subtypes of Vitamin KThere are several subtypes of Vitamin K.

Vitamin K1 (phylloquinone), found in plant sources such as green leafy veggies (specifically from their chlorophyll), accounts for about 75% of dietary Vitamin K intake. Absorption of Vitamin K1 from food sources isn’t very high, though it increases when combined with fat.

Vitamin K2 includes several subtypes called menaquinones. Each is called MK-n, where the number n refers to the number of repeated 5-carbon units connected to the core molecule, ranging from MK-2 to MK-13. Vitamin K2 is apparently more efficient at activating proteins that require Vitamin K than is K1.

The body can make most of the various menaquinones from phylloquinone via the gut flora, assuming the microbiome is healthy and diverse. However, the bioavailability of gut flora-produced K2 to other parts of the body is limited, so we still get most of our menaquinones from our diets. The most bioavailable K2 subtype is MK-7.

Menaquinones can be consumed from fermented foods and animal products. MK-4 is the only menaquinone that cannot be produced via the gut flora, and must be obtained from dairy products and some types of meat. (Vegans therefore might need to supplement.)

Vitamin K3, menadione, is a synthetic intermediate between K1 and K2, and is often used as an additive in animal feed.

Vitamin K DeficiencyBetween all the various food sources, Vitamin K deficiency isn’t super common. However, it can occur in those with malabsorption issues, such as IBD or celiac disease. Those with poor gut flora diversity in general may struggle with converting K1 to K2 as well. High doses of other fat-soluble vitamins (A or E) may also make it more difficult for the body to absorb Vitamin K.

In particular, there is a concern for newborn babies in the first 6 months of life, because of limited transport of Vitamin K across the placenta, low Vitamin K storage in the liver, immature gut flora (the gut is sterile at birth, and is initially populated via vaginal flora in a vaginal birth, but this won’t happen with a C-section), and also due to low levels of Vitamin K in breast milk. In premature infants, there is also concern that the Vitamin K cycle may not yet be fully functional.

These are the reasons why a Vitamin K shot is recommended at birth, to avoid any occult bleeds that might occur secondary to deficiency. There is some debate and concern over this shot, largely due to additives in the injection. Oral (sublingual) supplementation is an alternative option that does appear to be effective, according to some studies, as long as it is given on a regular basis during the first 6 months of life, and not simply one time at birth.

Toxicity from Vitamin KWhile allergic reactions can occur in response to Vitamin K, there is no known toxicity associated with high doses of either Vitamin K1 or K2. Toxicity can occur with the synthetic K3, though it is not typically used in humans.

Vitamin K and its Subtypes